Overplating needed 2.5yrs after good survey?

[magictime]

Hi all - this is my first post!

 

I'm not sure what to make of this and would appreciate some input.

 

We have a mid-90s 24ft Midway narrowboat, originally built with 4mm base plate and sides. We had a hull survey carried out when we bought her in early 2011 that revealed the steel thickness was down to 3.5mm in places, but the surveyor seemed happy with this and told us the boat should be good for another 20 years. She was blacked (baseplate included) and had new anodes fitted at that time.

 

Anyway, we've just had her in for blacking and repainting and the boatyard staff have advised us that the base plate steel is now very thin (1-2mm) around the edges - due to rubbing damage rather than corrosion - and so we might want to consider overplating the base plate.

 

This is (as far as I know) a reputable company that's done a good job of painting and blacking the boat at a fair price, and they haven't given us the 'hard sell' on overplating, so I've no reason to think they're being dishonest. And the base plate has certainly had a fair few scrapes over the past couple of years, usually as we've gone to moor up and found submerged rocks lurking under the surface at the canal edge. But it seems bizarre that the steel has got so thin so quickly - 0.5mm lost in c.15 years and then 2mm in c.30 months?

 

I'm now left wondering what to do, and how urgently to do it. If take their word for it and leave the boat with them for overplating, I'm going to be seriously out of pocket and our cruising plans for next year are going to be thrown into doubt (as we're going to be stuck the wrong side of a planned stoppage till March). If I arrange a survey to get a second opinion, that's another £200+ quite possibly on top of the overplating costs. One option might be to just cruise for the few days needed to get us the right side of that planned stoppage and on to another boatyard that can do overplating - but if the steel thickness really is down to 1-2mm in large areas, I don't know if we should be cruising at all.

 

Any thoughts? Does any of this have anything to do with a 'sacrificial chine' (it seems like it's that overhanging bit of the base plate that is visibly thin)? What would everyone else do?

 

Thanks!

 

 

 

 

 

 

[smileypete]

He magictime and welcome to the forum

 

How do the yard know it really is down to 1mm or 2mm?

 

If you do not want to spend £££ on another survey you could drill in those exact spots with a 1/4" drill bit to see how thick it really IS, if it is indeed 1 or 2mm then replating is money well spent, if it's nearer 4mm then it's another matter, just get the holes welded back up (for free? ) by the yard.

 

Usually an accurate hull thickess measurement involves the right ££££ ultrasound tester in the right hands.

 

cheers, Pete.

~smpt~

Edited December 7, 2013 by smileypete

[ditchcrawler]

I think they could only have been looking at the thickness of the base plate where it protrudes outside the hull as that is the only place you could see the thickness, how far this is worn under the boat is another matter. Pity they didn't call you to look at it before they refloated the boat.

[frangar]

Is it just the chines that are worn? Or the whole baseplate....which seems unlikely.

 

My boat is quite deep draughted and has some wear on the chines where we drag the bottom but is still ok after 30 years and we only have a 6mm baseplate.

 

If it's just the chines then you could just have some wear strips welded along the edges which could be easily removed should the whole baseplate need over plating at some point.

 

Cheers

 

Gareth

 

Edited to add....Ditchcrawler beat me to it!!

Edited December 7, 2013 by frangar

[Stilllearning]

Hello and welcome.

If as you say the wear is at the edge of the baseplate, then I imagine what the yard is talking about is indeed wear to the edges, at the "corners" where the front and back swims begin/end.

If that is the case, then just a short length welded on the underside of the baseplate will be enough to solve the problem.

Yards tend to err on the side of caution when they see wearing baseplates.

Hope this helps.

[alan_fincher]

I don't know much about the midway boats, bur was a boat built in the "mid 90s" really only built with 4mm plate for the hull sides and baseplate?

 

OK, I can see this is quite a small boat, but I would say it was fairly unusual for anything to be built that thin that late on, wasn't it?

 

Can anyone confirm that is the "usual" spec for a Midway boat that is 20 years old, or less, please?

[Graham Davis]

We looked at Midway boats at one stage, and that specification sounds correct for their small boats.

[magictime]

Thanks for your input everyone.

 

Alan, we've never been very sure on the date the boat was built, but I've seen other boats of the same model (the 235) for sale that were built in the mid 90s. I suppose Midway were trying to fill the gap in the market left behind by Springer.

 

Everyone seems to be thinking along the same lines - i.e. if it's just the edges/chines that are worn, overplating the whole base plate sounds like overkill. But I did ask about the possibility of a less drastic solution and the boatyard didn't seem too keen on the idea. Why, I don't really know - no doubt they'd have some technical explanation.

 

I think I'm going to have to get that second opinion from a surveyor, but of course the risk there is that even if he suggests a less drastic option than overplating, the cost of that less drastic option plus the cost of the survey could end up being close to the cost of overplating.

 

And ditchcrawler - yes, I wish they had raised the alarm while she was out of the water. Then we could have taken a look ourselves, got a surveyor out, and done any work that needed doing without having to lift her out again. Why they didn't do so, I've no idea. They pretty much just mentioned this in passing when we went to pick the boat up - which seems weird to me, because I'd have thought having a 1mm base plate was quite a big deal!

 

Anyway - in the short term, what do people think about the wisdom of cruising? Would you be happy to travel on your boat if you'd been told the edge of the base plate was down to 1mm, or would you be leaving it at the boatyard till it was sorted one way or another?

 

Thanks again.

[alan_fincher]

I'm really struggling to see how steel measured at 3.5mm less than 3 years ago can now be down to 1mm.

 

Seems odd to have only lost a maximum of 0.5mm in (say)16 years, but have lost 5 times that amount in less than 3 years since then.

 

Particularly so, if the claim is it is due to wear, rather than wastage due to corrosion.

 

I assume if you had been grinding it over countless rough bottoms you would know, but this sounds to me like a relatively shallow draughted boat where I'd expect to be dragging the bottom of the cut only very rarely.

 

Something is not right it seems to me - either the previous survey failed to find the thinner bits, or the view about current thickness is wrong.

 

How is the current thickness being measured?

[Neil2]

A boat that small built with anything thicker than 4mm is going to sit really low in the water, it just doesn't contain enough air. For this reason you can spot an overplated waterbug (also built with 4mm) dead easy - they are alarmingly low slung. Like waterbugs, I'll bet this boat carries no ballast at all, so if you overplate there is no way to avoid the boat being pulled down in the water.

 

If the yard were concerned about the chine wear why the hell did they put the boat back in the water without you having a chance to look at it?

 

Did they say the wear was the whole length of the chine? It's almost always confined to bow or usually stern area. How many boaters do you see setting off by pushing the bow away and jumping aboard? The edge of the stern chine catches on the side and that's what causes the wear.

 

I wouldn't worry about it for now, maybe be a bit more cautious when coming in to the side and setting off, and have it looked at again when she next comes out of the water. With a boat like this I'd black it yearly, that's what we did with our waterbug, which, incidentally is a better design for a small NB as they have a pronounced V hull which in normal circumstances will never suffer from abrasive wear.

 

 

[Keeping Up]

Our first boat had worn through at the edges, after many years on the Llangollen and Shroppie, until she sank. Strips of angle were welded along each side and they were fine for another 20 years until the base plate finally needed overplating.

[Timleech]

You really need to find out for certain just where they found this 1 to 2mm measurement. Were they actual measurements, and if so how taken?

If it really is actual plating thickness within the hull area, then yes it's cause for serious concern and it could be suggested that the yard were negligent in putting it back in the water without telling you beforehand.

If it's the exposed edge of the plate, that's rather different. It could still be cause for concern, but might be a lot less serious.

If it is just wear at the edges, with no other major worries (extensive corrosion, perhaps), then fully overplating the bottom is probably major overkill.

'Shoeing' along the edges will more than likely be sufficient, not much less welding but much less weight, less steel and less work.

Do make sure that any shoeing added is continuously welded all round, though, so that it becomes part of the hull rather than just a sacrificial strip. That's especially important if it really is as thin as they say.

 

Tim

[ditchcrawler]

Thanks for your input everyone.

 

Alan, we've never been very sure on the date the boat was built, but I've seen other boats of the same model (the 235) for sale that were built in the mid 90s. I suppose Midway were trying to fill the gap in the market left behind by Springer.

 

Everyone seems to be thinking along the same lines - i.e. if it's just the edges/chines that are worn, overplating the whole base plate sounds like overkill. But I did ask about the possibility of a less drastic solution and the boatyard didn't seem too keen on the idea. Why, I don't really know - no doubt they'd have some technical explanation.

 

I think I'm going to have to get that second opinion from a surveyor, but of course the risk there is that even if he suggests a less drastic option than overplating, the cost of that less drastic option plus the cost of the survey could end up being close to the cost of overplating.

 

And ditchcrawler - yes, I wish they had raised the alarm while she was out of the water. Then we could have taken a look ourselves, got a surveyor out, and done any work that needed doing without having to lift her out again. Why they didn't do so, I've no idea. They pretty much just mentioned this in passing when we went to pick the boat up - which seems weird to me, because I'd have thought having a 1mm base plate was quite a big deal!

 

Anyway - in the short term, what do people think about the wisdom of cruising? Would you be happy to travel on your boat if you'd been told the edge of the base plate was down to 1mm, or would you be leaving it at the boatyard till it was sorted one way or another?

 

Thanks again.

I would be very surprised if the boatyard measured anywhere except the edge, they probably only work on boats with 10mm base plates and went "O that looks thin"

[the grinch]

there is absolutely no way you can lose that amount of thickness in such a short time unless you use an angle grinder!! somebody is not telling the truth either it was thinner at first survey or the yard is exaggerating the current thinness!

[magictime]

Alan, I'm struggling to make sense of it for just the same reasons. But I have been aware of scraping over rocks etc. fairly often - usually when we've pulled in to moor up and found ourselves in shallow, rocky water, but sometimes just when a canal has been shallow. (The Rochdale springs to mind!) Our draft is around 2ft, I think - not that deep, but not that shallow either.

 

And Neil2, there's certainly been a certain amount of side-on scraping going on when pulling in and out at locks etc. - less so now I'm more confident handling the boat, but still...

 

So it's not utterly implausible that a fair amount of damage has been done fairly quickly, although I wouldn't have said the boat has had that rough a time of it.

 

They shouldn't have put it back in the water, that much is clear. In fact it seems to me that they shouldn't have blacked it before raising this issue. Surely if any welding/overplating was going to be done, it should have been done before the blacking?

 

I'm leaning more and more towards a hull survey as the only way to get to the bottom of this - especially having heard what you say about the downside of overplating, Neil2.

 

Thanks again everyone.

[Tuscan]

I agree with others something is not quite right here, I would be amazed if you have lost so much thickness. It seems that another conversation with the boat yard is needed to get them to explain more fully what hey found and where.

 

I suspect your trust in the yard has been damaged so I would be minded to get beyond the stoppage and speak to a couple of surveyors until you find one that understands your concerns and then if you can afford it get it checked so that you can sleep easy.

[Bee]

If the surveyor back in 2011 tested it ultrasonically he would probably have tested in various accessible points along the sides and base and found it ok, the yard however have just cast an eye over the edges, two different animals, if you are worried I would suggest the best way forward would be to have it looked at again by the first surveyor and tell him of your worries, also 26` is not a lot to overplate so don`t panic, I doubt there is a lot to worry about.

[Neil2]

I would be very surprised if the boatyard measured anywhere except the edge, they probably only work on boats with 10mm base plates and went "O that looks thin"

Yes - let's be honest, there's a new generation that think anything less than a 10mm baseplate is risky because that has become the norm. On small boats though it is bad design. A lot of boats under 40 foot can't be trimmed properly because of all the weight in the 10mm base plate.

 

If steel boat owners adopted the same practice as. say, wooden boat owners, ie lift her out every year, there would be no need for the widespread paranoia regarding hull thickness. Seems to me narrowboats these days are designed/built on an assumption that the owner(s) will do as little maintenance as possible, which is probably true.

If the surveyor back in 2011 tested it ultrasonically he would probably have tested in various accessible points along the sides and base and found it ok, the yard however have just cast an eye over the edges, two different animals, if you are worried I would suggest the best way forward would be to have it looked at again by the first surveyor and tell him of your worries, also 26` is not a lot to overplate so don`t panic, I doubt there is a lot to worry about.

As I said earlier, overplating a small boat, say under 30' is a risky business - the fact that it might be cheaper than a big boat is irrelevant.

[magictime]

Just a quick update.

 

I spoke to our surveyor and he's very sceptical that any significant wear has happened since he looked at the boat in 2011. He also said it's not unusual for the protruding edge of the base plate to get quite thin, since it's exposed to the water on two sides, and this is not a problem since this isn't a structural part.

 

Putting two and two together, I'm fairly confident that the boatyard are just overreacting to a protruding edge that (1) is only about as thin as you'd expect it to be on a 15-year-old boat with a 4mm base plate, and (2) says very little about the likely thickness of the rest of that base plate. All in all, I'm inclined to think that the 2011 survey remains a more reliable guide to the hull condition.

 

I've asked the boat yard if they'd be willing to lift the boat back out of the water for free (on the basis that they should never have put it back in if they had this sort of concern). If they agree to that, I'll get the surveyor to take a look just to be on the safe side. But if not, I'm not inclined to do anything more about it until the boat is next out of the water for blacking.

 

False alarm, I reckon.

[junior]

Call me a cynic, but this sounds a bit like the boat yard may have been trying to generate themselves a bit of work.

[Tom Richmond]

I was going to suggest that you push the boat yard for a free lift out... After all they are the ones expressing concern, they refloated it when they possibly shouldn't have, and if you do find a problem, they will get work out of it anyway!

 

Make sure you know who's paying for the lift back in as well (should probably be them)!

 

Best of luck...

[Captain Fizz]

I would be very sceptical of the proficiency of any yard who returned a boat to the water with such apparently thin areas without first contacting the owner for instruction.

Junior maybe on the right track.

Use it for the next season and have another look next year.

[Robbo]

Just a quick update.

 

I spoke to our surveyor and he's very sceptical that any significant wear has happened since he looked at the boat in 2011. He also said it's not unusual for the protruding edge of the base plate to get quite thin, since it's exposed to the water on two sides, and this is not a problem since this isn't a structural part.

 

Putting two and two together, I'm fairly confident that the boatyard are just overreacting to a protruding edge that (1) is only about as thin as you'd expect it to be on a 15-year-old boat with a 4mm base plate, and (2) says very little about the likely thickness of the rest of that base plate. All in all, I'm inclined to think that the 2011 survey remains a more reliable guide to the hull condition.

 

I've asked the boat yard if they'd be willing to lift the boat back out of the water for free (on the basis that they should never have put it back in if they had this sort of concern). If they agree to that, I'll get the surveyor to take a look just to be on the safe side. But if not, I'm not inclined to do anything more about it until the boat is next out of the water for blacking.

 

False alarm, I reckon.

 

If they don't offer a free lift out then I wouldn't use the yard again! Ask them how they know it was thin. These metal thickness detectors really only work on the flat areas so on a edge they won't. If they got a hammer and whacked it then it's a good sign as you can tell how thin it is by how much it's denting!